1. Field of the Invention
The present invention relates to a gallium phthalocyanine compound useful for a photosensitive material for electrophotography, a material for a photoelectric conversion element, and a material for an organic semiconductor element, and also relates to a gallium phthalocyanine composite pigment, a method for preparing a gallium phthalocyanine composite pigment, and an electrophotographic photoconductor.
2. Description of the Related Art
A phthalocyanine compound is an effective material widely used as a coating material and an electronic material. In recent years, the phthalocyanine compound has been studied and researched particularly for various applications such as a photosensitive material for electrophotography, a photorecording material, and a material for a photoelectric conversion element. As photosensitive materials for electrophotography, there are numbers of proposals for use of a phthalocyanine compound that has photosensitivity in the near infrared wavelength region of a semiconductor laser. Crystal shapes of the phthalocyanine compound have been intensively studied for improving an electrophotographic photoconductor in terms of both sensitivity and stability during the use of a long period. It has been known that the phthalocyanine compound generally forms various crystal shapes thereof depending on the preparation methods or treating methods, and that the difference in the crystal shapes thereof gives a great influence to photoelectric conversion efficiency of the phthalocyanine compound and stability of the resulting photoconductor in repeated use. For example, in the case of copper phthalocyanine, as crystal shapes of the phthalocyanine compound, other than stable β-type, crystal shapes of α, π, χ, ρ, γ, and δ have been known, and it has been also known that these crystal shapes are interchangeable by the application of external physical force, sulfuric acid treatment, organic solvent treatment, or thermal treatment. The descriptions related to a gallium phthalocyanine compound can be found in Japanese Patent Application Laid-Open (JP-A) Nos. 05-98181, 05-263007, 07-53892, and 2009-62475.
As mentioned above, it has been desired that a charge-generating material used for an electrophotographic photoconductor be highly sensitive in a wide wavelength range, and stably exhibit electrophotographic characteristics. Especially, a phthalocyanine pigment tends to have a problem in dispersibility or a stability of the resulting coating liquid because the phthalocyanine pigment is dispersed at the time of use. It is a current situation that it has not been developed a charge-generating material comprehensively satisfy the aforementioned characteristics.